Radio Block Centre (RBC)
A Radio Block Centre is the trackside computer in ETCS Level 2 and Level 3 that issues movement authorities to trains over radio. It takes track occupancy and route status from the interlocking, tracks each train's reported position, and calculates how far and how fast each train may safely travel.
How it works
Trains report their position to the RBC over GSM-R or FRMCS using the Euroradio protocol, which adds a cryptographic safety layer to the radio link. The RBC combines these reports with the state of the interlocking (locked routes, point positions, occupied sections) and returns a movement authority: the distance the train may proceed and the speed profile it must respect.
Each RBC covers a defined area of the network. When a train approaches the boundary, the handing-over RBC and the accepting RBC coordinate so the movement authority continues without a gap. The RBC also manages key exchange with onboard units, emergency stop messages and the transition between ETCS levels.
Why it matters for security
The RBC sits at the meeting point of three networks: the radio system, the interlocking and the operator's maintenance and diagnostic infrastructure. A compromised or spoofed RBC could withhold or falsify movement authorities for every train in its area, so it is among the highest-value assets in an ERTMS deployment.
Because RBCs are certified safety systems, they cannot be patched or scanned like ordinary servers. Security therefore depends on isolating them, controlling the interfaces around them and monitoring the traffic they exchange with interlockings, neighbouring RBCs and the radio core.
Related solution
Operating ERTMS across national rail networks
Monitoring RBC, interlocking and radio-core interfaces without touching certified equipment.
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